Temperature, Humidity, Ventilation
It is interesting to note that orchids flourish in the same temperature that we humans enjoy. During the day time, they are comfortable when the temperature ranges between 70°F and 80°F (21°C and 27°C), while at night they prefer a temperature range of 10°F and 15°F (5°C and 9°C).
When you go through the catalogs of orchids, you will come across terms such as cool-growing, warm-growing and intermediate. All these terms denote the minimum night time temperature during the winter that the orchid species favour. In other words, these are the minimum temperatures that the orchid species are able to endure.
Orchids that have been termed as cool-growing thrive best when the night time temperature is between 50°F and 55°F (10°C and 24°C) and when the daytime temperature ranges between 60°F and 75°F (16°C and 24°C). The cool-growing orchids include odontoglossums, cymbidiums, masdevallias and several paphiopedilum orchids.
A number of cool-growing orchids are capable of enduring night temperatures that as low as in the 30°s Fahrenheit (-1°C to +2°C). Therefore, it is not surprising that it is quite difficult to grow these orchids in places where the temperatures are always high during the summer months.
However, a number of individual cool-growing species are also capable of enduring higher temperatures. Orchid species that thrive well in intermediate temperature include cattleyas, several oncidiums, dendrobiums, paphiopedilums and even a vast number of supposed species or botanical orchids.
The intermediate temperature that we are talking about here ranges between 55°F and 60°F (13°C and 16°C) during the night time and between 65°F and 80°F (19°C and 27°C) during the daytime. On the other hand, warm-growing orchids include phalaenopsis, vandas and a number tropical paphiopedilums.
These orchid species enjoy growing in temperatures between 60°F and 65°F (16°C and 18°C) during the night and between 70°F and 85°F (21°C and 27°C). Many orchid plants will go through distress when the temperatures rise above a certain point for a prolonged period.
When there is bright sunlight along with intense heat, the leaves of orchids will display sunburn – they will have bleached areas that would eventually turn brown or even black. What is worse is that the leaves may fall depending on the severity of the damage.
In extreme situations even result in the death of the plants. In addition, intense heat and powerful light may also induce transpiration in the plants, wherein they lose dampness through their leaves and this proves detrimental for them.
It is worth mentioning here that in several instances even if the orchids do not appear to be sunburned or stressed in any other manner; they will not be able to prosper when the temperature is too high. In such cases, they will develop a yellowish hue and stop growing further. Some orchids may even stop flowering in such situation.
However, most orchids will not be harmed due to high temperatures provided they are grown under some shelter and away from direct sunlight. At the same time, they need to be provided with enhanced humidity when the temperatures soar.
When the temperature is around 90°F (32°C) during the day, it is, in fact, advantageous for the some plants, particularly warm-growing orchids. Many hobbyists take their orchids indoors during the summer months. Inside their homes, the plants are kept in dappled shade and in well ventilated spots thereby creating the environment they actually enjoy in their native habitats.
Aside from the right temperature, another important factor necessary for the health of the orchids and to enable them to thrive is atmospheric humidity or the percentage of water/ moisture present in the air. While nearly all orchids have a natural growth in humid environments, when grown indoors, they can thrive with only 30 percent to 40 percent humidity.
In fact, most people are also comfortable with this level of humidity. On the other hand, lower level of humidity is as harmful for orchids as are intense heat and strong light. When the humidity rate is low, it will prompt the plants to transpire more. However, when the humidity is poor you may increase it by using portable electric humidifier.
You may incorporate the humidifier unit in the central heating forced-air furnace. Alternatively, you may also place a gently steaming kettle on the stove near the orchid. When the temperature increases indoors you should compensate it by increasing the humidity level.
On the other hand, when the temperature drops during the evening, you need to adjust the environment by decreasing the humidity level. These will help the plants remain disease free and also prevent the organisms that are responsible for various diseases from affecting your orchids.
It is worth mentioning here that such organisms thrive in conditions wherein the temperatures are low and the humidity levels are high. There are many orchid growers who maintain the right humidity for their plants by placing them on trays or pots that filled with water and gravel.
As water evaporates from the wet gravels, the humidity around the orchids is increased to the optimum level, helping the environment remain moist as well as fresh. However, you need to ensure that the water in the tray does not rise to the level of the pot. At the same time, stagnant water may cause the orchid roots to rot.
Another way to maintain the right level of humidity is to grow several plants in close vicinity, as the moisture transpired by one plant will be shared by the plant in its neighbourhood. When the environment inside the room becomes arid, you should spray your orchids using a fine mist of water.
This is an excellent way to supplement the humidity in the environment. However, ensure that the mist is fine enough to leave behind a thin film on the leaves that would evaporate quickly. When you use a coarser spray it may lead to problems by steeping the plant, planting mix as well as the pot.
Ideally, the orchids should be sprayed on early in the day so that the surfaces of the leaves and the crowns of the plants dry out much before it is evening. This is particularly vital when you are spraying phalaenopsis (also known as moth orchids).
In addition to the above mentioned factors responsible for healthy growth of orchids, proper ventilation is equally important for the plants to thrive well. Free circulation of air around the orchids is important because when the air is stagnant it has a tendency to trap heat around the surfaces of the leaves.
During the summer months, the ventilation in your home is generally acceptable as windows are open almost throughout the day. In places where you require air-conditioning during summer, or where you are unable to keep the windows open during the winter, you may possibly need a small oscillating fan to ensure that the air circulates properly, thereby promoting the growing conditions for your orchids.
However, it is important not to direct the fan towards the orchids because the plants will not tolerate drafts. Ideally, you should position the fan such that the air flow is directed either above or below the plants.
If there is an air-conditioning or forced air-heating duct just below the window where you have placed your orchids, you should cover the duct using a deflector so that the air is directed into the room, but away from the orchids.
Your orchids will benefit if you keep them outdoor under some shade during the summer months in nearly all climatic conditions. When the plants are left outdoors, they will receive fresh, circulating air as well as a humidity level that they prefer. In addition, they would be cleansed occasionally by rains.